Neutrophil gelatinase-associated lipocalin as an early indicator for mortality in adult critically ill patients with acute kidney injury

Abstract

Introduction: Neutrophil gelatinase-associated lipocalin (NGAL) measured in plasma or urine has shown to be an excellent early predictor for the development of acute kidney injury (AKI) [1]. Furthermore, AKI is an independent risk factor for mortality in critically ill patients [2]. We therefore hypothesized that NGAL concentrations measured at ICU admission in plasma and urine are associated with mortality. Methods: We collected plasma and urine samples at ICU admission from all consecutive admitted patients (n = 700), of whom 171 during their first week of admittance, meeting criteria for any stage of AKI according to RIFLE classification for serum creatinine (sCr) increase only. NGAL concentrations were measured using a rapid immunofluorescence assay (Triage meter plus; Biosite Inc., San Diego, CA, USA). The Mann-Whitney U test was used for comparison of mean NGAL concentrations in plasma and urine between survivors and nonsurvivors. Exclusion criteria were patients with a history of nephrectomy, chronic or end-stage renal disease, kidney transplant surgery and informed consent refusal (n = 36). Results: One hundred and seventy-one patients met criteria for AKI and were included in the statistical analysis. Median (25th to 75th percentile) age (years), APACHE II score after 24 hours and on admission sCr concentrations for survivors (n = 105) and nonsurvivors (n = 66) were respectively 59 (46 to 68) and 64 (53 to 73), 21 (15 to 26) and 26 (22 to 31), and 65 (60 to 80) and 80 (65 to 100) mumol/l. Median (25th to 75th percentile) NGAL plasma and urine concentrations were respectively 300 (160 to 504) ng/ml and 426 (127 to 1,543) ng/ml for the survivors and 457 (281 to 991) ng/ml and 1,189 (381 to 4,124) ng/ml for the nonsurvivors. These differences for both plasma and urine NGAL values were statistically significant (both P <0.005). Conclusions: Plasma and urine NGAL concentrations at ICU admission are significantly higher in nonsurviving patients compared with concentrations in surviving patients. Therefore NGAL measured at admission might be an early indicator for mortality.